What is equilateral triangle ?
In geometry, an equilateral triangle is a triangle in which all three sides are equal. The area enclosed by this shape is known as area of equilateral triangle.
Area of equilateral triangle can be found using the formula given below.
Area of Equilateral Triangle = (√3/4)a^{2 }sq. units
where a is the length of each side of the triangle.
Take an equilateral triangle of the side “a” units. Then draw a perpendicular bisector to the base of height “h”.
By drawing perpendicular from A, we get two congurent right triangle ABD and ADC.
Area of triangle ABC = Area of triangle ABD + Area of triangle ADC
Since triangles ABD and ADC are congurent, areas will be equal.
Area of triangle ABC = Area of ABD + Area of ADC
Area of triangle ABC = 2 (Area of ABD)
= 2 ⋅ (1/2) ⋅ Base ⋅ Height
Area of triangle ABC = Base ⋅ Height ---(1)
In triangle ABD,
Base (BD) = a/2 and height (AD) = h
Using Pythagorean theorem,
a^{2} = h^{2} + (a/2)^{2}
h^{2 }= a^{2 }- (a^{2}/4)
h^{2 }= (3a^{2}/4)
h = √(3a^{2}/4)
h = (a√3/2)
By applying the values of base and height in (1), we get
Area of triangle ABC = (a/2) ⋅ (a√3/2)
= (1/4)a^{2}√3
Area of triangle ABC = √3a^{2}/4 square units
Example 1 :
Find the area of the equilateral triangle having the length of the side equals 10 cm.
Solution :
Area of equilateral triangle = (√3/4) a²
Here a = 10 cm
= (√3/4) (10)²
= (√3/4) x (10) x (10)
= (√3) x (5) x (5)
= 25 √3 cm²
Example 2 :
Find the length of the altitude of an equilateral triangle of side 3√3 cm.
Solution :
Side length of equilateral triangle (a) = 3√3
Area of equilateral triangle = (√3/4) a²
= (√3/4) (3√3)²
= (√3/4) (27)
Area of equilateral triangle = 27√3 / 4 ---(1)
Here we should find the length of altitude, so we use the formula base ⋅ height to find the area of equilateral triangle.
= base ⋅ height
= (3√3/2) ⋅ h ------(2)
(1) = (2)
(3√3/2) ⋅ h = 27√3/4
h = (27√3/4) ⋅ (2/3√3)
h = 9/2
h = 4.5
So, the required height is 4.5 cm.
After having gone through the stuff given above, we hope that the students would have understood how we derive the formula for area of equilateral triangle and examples.
Apart from the stuff given in this section, if you need any other stuff in math, please use our google custom search here.
Kindly mail your feedback to v4formath@gmail.com
We always appreciate your feedback.
©All rights reserved. onlinemath4all.com
May 30, 23 11:19 AM
May 30, 23 10:38 AM
May 26, 23 12:27 PM